1. Field of the Invention
The present invention relates to a sheet feeding apparatus for feeding a sheet, e.g., a recording sheet, to an image forming apparatus or the like, and an image forming apparatus having the sheet feeding apparatus.
2. Related Background Art
FIG. 15 is a perspective view showing the schematic arrangement of a conventional sheet feeding apparatus.
As shown in FIG. 15, the conventional image forming apparatus such as a printer has a sheet feeding apparatus 121 for feeding sheets one by one to an image forming unit such as a recording unit (or printing unit). In such a sheet feeding apparatus, a feed roller 102 is brought into pressure-contact with a sheet to provide a convey force, and a separation means constituted by a separation pad, separation pawl, separation bank, and the like is used to provide a convey load, thereby separating only one sheet from the second and subsequent sheets.
As shown in FIG. 15, the sheet feeding apparatus 121 having such a separation means includes a roller shaft 131 pivotally supported on a base 140, feed roller units 130 and 130′ inserted in the roller shaft 131, and a hopper 103 which is pivotally mounted on the base 140 and comes into contact with/separates from the feed roller 102. A side guide 132 is mounted on the hopper 103. The side guide 132 can move in the sheet widthwise direction in accordance with the width of a sheet bundle stacked on the hopper 103.
The second feed roller unit 130′ moves together with the slidable side guide 132. The position of the first feed roller unit 130 is fixed.
Such a sheet feeding apparatus requires a space in which the second feed roller unit 130′ moves. When a wide sheet bundle such as an A3-size sheet bundle is stacked, in particular, it is difficult to ensure a sufficient support area for the leading edge middle portion of a sheet bundle in the hopper 103. As shown in FIG. 15, therefore, the hopper 103 has a rotating support member 150, in the space in which the second feed roller unit 130′ moves, to support the leading edge middle portion of a sheet bundle.
With this arrangement, when the side guide 132 is aligned with a wide sheet, the leading edge middle portion of the sheet is supported by the rotating support member 150. In addition, when the hopper 103 so pivots as to come into pressure-contact with the feed roller 102 in feeding operation, the leading edge middle portion of the sheet bundle is supported by the rotating support member 150. When the side guide 132 is aligned with a narrow sheet, the rotating support member 150 comes into contact with the second feed roller unit 130′ and pivots about a shaft 150a in a direction S in FIG. 15 to be accommodated in the hopper 103. This makes it possible to ensure a space in which the second feed roller unit 130′ moves.
The rotating support member 150, however, only supports the leading edge middle portion of a sheet bundle in an auxiliary manner. For this reason, the state of the leading edge of a sheet that is separated after feeding operation becomes unstable because convey routes are different between the two ends and the middle portion in the sheet widthwise direction. As a consequence, the sheet may skew and be conveyed to a wrong position.
When the side guide 132 is aligned with a narrow sheet, since the sheet bundle tends to be caught in the recess portion where the rotating support member 150 is housed, the sheet bundle is reluctant to be stacked in the hopper 103.